The Sun and the Morning Star
by The Dimension Crossing Mew
Summary: Somebody is killing duelists in Battle City San Diego. Despite opposition from Seto Kaiba, the BAU has been called in to find the killer. Now, the duelists are threatening to riot if the tournament shuts down, Kaiba is stonewalling the BAU, and the King of Games and his friends are more than they seem. Add in deadly magic and ancient gods, and the BAU might be in over their heads.
1. Prologue

**San Diego**

The man looked on in disbelief as his last monster burst into colorful pixels and his life points reached zero. He dropped to his knees in the dark alleyway, muttering, "No," over and over before he quieted, eyes blank.

A shadow stalked towards the defeated duelist. Silver moonlight glinted off of the blade of an upraised stone knife. The knife slashed down, and a spray of dark blood spattered the walls and ground of the alley. The sound of flesh parting, the murmur of foreign words, a flare of a match. These were all there and gone in a minute.

Only a few minutes later someone else walked onto the alley. " _Doko wa_ …" the young woman murmured, looking for the light that had drawn her out of her hotel room and to the alleyway. She stepped further into the alley, and that's when she saw the grisly scene.

Stumbling back with a curse, she pressed the emergency button on her Duel Disk. As she waited for the Kaiba Corp security team to respond, she looked on in horror at the body of the other duelist, his chest torn open, heart burning on the dirty concrete. Even as she heard sirens approaching, she couldn't look away.


	2. Ce Miquiztli

_When walking through the 'valley of shadows,' remember, a shadow is cast by a Light._

 _\- Austin O'Malley_

Crime scene photos and images of victims were already up on the screen as the team of FBI profilers filed in. Technical Analyst Penelope Garcia, clad in a vividly colored floral print dress with matching high heels, lipstick, and flower hair clip, waited until all the agents were seated before starting the presentation.

"Ok, so, we have a case in San Diego," Garcia began. "In the past week, five people have been found dead in San Diego's Gaslamp Quarter." A click of her remote had the photos cycle past, one after the other. The victims were both men and women of differing ages and ethnicities, their rib cages torn open to expose the chest cavity, a charred lump by each body.

"Each victim had their chest cut open and their heart cut out and burnt," Garcia continued. "And can I just say, 'eww.' I mean, seriously, who does that?"

"Five victims, with ritualistic overtones," David Rossi said. "Why weren't we contacted earlier?"

"And that's where things get complicated," Garcia admitted.

"Each of the victims was a registered competitor in Battle City San Diego," Unit Chief Aaron Hotchner explained. "Seto Kaiba, another competitor as well as the organizer and sponsor of the tournament, refuses to allow any investigation that could seriously interrupt or prematurely end the competition."

"What sort of person cares more about a game than people's lives?" Derek Morgan demanded.

"One with an ego as big as his bank account, apparently," Jennifer 'JJ' Jareau answered. "Seto Kaiba is the youngest CEO and billionaire in the world."

"He was also the youngest Duel Monsters World Champion," Spencer Reid remarked.

"Duel Monsters? You mean that card game that most of the world is obsessed with?" Alex Blake asked.

Reid nodded and leaned forward. "It was created by Pegasus J. Crawford and originally marketed to adult gamers as 'Magic & Wizards.' It grew really big here in the US among older gamers, but it didn't really get much attention from the younger generation until Kaiba won the World Championships. The largest concentration of top-ranked duelists is currently in Japan, but its popularity was fairly niche there until Yugi Mutou defeated Kaiba in his debut duel."

"Mr. Kaiba has been trying to keep the murders as quiet as possible," Hotch said. "The first four victims were all foreign nationals, but the last victim, Brian Donnelly, was an American citizen. Kaiba Corp is allowing Garcia to look at their systems under supervision, and the remaining duelists have all been asked to gather at the San Diego Convention Center to be interviewed. Get your things ready; wheels up in thirty."

On the jet, conversation quickly turned to Duel Monsters.

"So, you seem to be well informed on the Duel Monsters phenomenon," Rossi remarked, taking a seat across from Reid. "Do you happen to be a duelist yourself?"

"No," Spencer answered. "Unfortunately, I never had the money to build a proper deck, or even buy a pre-built starter deck. Dueling can be remarkably expensive if you want to have a good deck."

Morgan, walking by, cuffed Reid's shoulder. "You mean to tell me that there's actually a card game that our Pretty Boy doesn't play?" he joked, sitting next to Reid.

"Not with real cards," Reid admitted. "A single booster pack might not cost much, but there's no guarantee that any of the cards will be good. It's why so many second generation duelists use handed down decks."

"Second generation duelists," Rossi repeated, eyebrow raised.

"Duel Monsters has been around long enough to have second, and even third, generation duelists. Both Rebecca Hawkins, the current American champion, and Yugi Mutou, the reigning Duel King, use decks that originally started out as their grandfather's," Reid elaborated. "That's why I find it easier to use online free-to-play sites, instead."

"You talking about Duel Monsters?" Garcia asked, taking a seat next to Rossi. "Don't let Reid's innocent act fool you; he's a total boss on DuelPro."

"I'm not all that good, really," Reid protested.

"Sweetie, if you were to ever shell out for a decent deck, you'll be a top-ranked duelist in no time," Garcia insisted.

Morgan leaned back in his chair, arms crossed. "Alright, Baby Girl. What have you gotten from Kaiba Corp so far?"

"Absolutely nothing. Nada." Despite her words, Garcia was grinning broadly. "I've never seen firewalls as sophisticated as Kaiba Corp's. Not even the _Pentagon_ is so secure. I knew that Seto Kaiba was a genius, but he's a GOD when it comes to coding."

"Seriously?" Morgan scoffed in disbelief. "You, Penelope Garcia, the FBI's Computer Goddess, out done by a teenager half your age?"

"A teenager with enough patents to his name to impress even Tony Stark, if he existed," Garcia retorted. "There's a reason why I'm coming with you, even though I hate being out in the field."

The conversation turned to small talk after that for the rest of the flight. When they landed in San Diego, they found that Kaiba Corp had sent a limousine to take them straight to the Convention Center, where they were met by a teenager _other_ than the one they were expecting.

"We were told that Mr. Kaiba would be meeting with us immediately," Hotch stated, coldly staring down the short teenager that stood before them.

The dark-haired teen met Hotchner's stare with an icy glare of his own. " _Nii-sama_ is busy," he replied in accented English. "He's asked me to meet you in his place." He turned, dark-suited bodyguards falling in around him. "If you would follow me, I'll take you to the rooms you can use for interviews."

"What's the deal with this kid?" Morgan muttered, watching the retreating back of the boy.

"That's Mokuba Kaiba, Seto Kaiba's little brother," JJ whispered back. "He's also the Vice President of Kaiba Corp and the gaming commissioner for Battle City."

"That little kid?" Derek was incredulous.

"He's a genius, like his brother, and the Capsule Monsters World Champion," Reid said.

"There is something off with that family," Morgan commented.

"And you haven't even seen Kaiba's infamous Blue Eyes White Jet," Reid joked. Morgan just shook his head as the team followed Mokuba.


	3. Ome Tequani

**AN:** I'm not entirely happy with this chapter, but I needed an outside point-of-view that still made it obvious that the events of the Yu-Gi-Oh manga are not actually happening in a vacuum. _Somebody_ had to notice what was going on, even if they don't quite understand it. Also, the manga made it seem ridiculously easy to find out about the Millennium Items, to the point where apparently random characters know about them.

* * *

Hotchner had decided, once they got some of the smaller conference rooms set up, that Rossi and Reid would interview the duelist that had found the last victim.

The young lady that was let into the room looked like a wild woman. Her long black hair was a wild mane. At her wrists were brown fur cuffs, with matching fur trim on her clothes. There was a bear claw necklace around her neck, and silver claws tipped the fingers of her left hand.

"Do you need a translator?" Rossi asked as the young Japanese woman sat down across from him and Reid.

"No. I speak English," she replied haltingly. "Need practice, but I can speak," she added, shrugging a shoulder.

"I'm Agent David Rossi, of the FBI, and this is my colleague Dr. Spencer Reid," Rossi said, glancing through the file in front of him. "Your name is Kumako Morimura, correct?"

" _Kumako janai yo!_ " Her voice was stern in her denial. "I prefer 'Kuma,' but am best known as 'Grizzly' Kuma." Kuma enunciated the word 'grizzly' carefully.

"Grizzly bear?" Reid translated. "How did you pick up _that_ name?"

Kuma unsnapped the deck holder on her belt and pulled out the deck of cards. She shuffled the deck with deft hands. "I play Beast deck," she commented, setting the shuffled deck on the table. "Among duelists, there is concept of ' _kokoro no kaado,_ '" she started to explain. "This can mean 'heart of the cards'; the belief that if you have faith in your deck, you will always draw what you need." Her pronunciation grew better as she got used to speaking English, the words coming to her more easily than before.

Kumar continued "This can also mean 'card of the heart'; the card that most, uh, _resonates_ , with a duelist. For _Kaiba-san_ , this is Blue Eyes White Dragon. For _Kujaku-san_ , this is Harpy Lady. For me," she drew the top card of the deck, laying it face up beside the deck, "this is Mother Grizzly."

For a brief second, Reid thought he felt fur brush against him. The next moment he could have sworn he saw a great bear at Kumo's side, the image there and gone in a heartbeat. He shook his head, trying to convince himself that it had just been his mind playing tricks on him.

Kuma watched the two FBI agents carefully. The older man was obviously skeptical, one eyebrow raised. The younger one had the look of a gamer and was looking thoughtfully at the Monster card.

The young woman could admit, if only to herself, that she had been nervous about talking to the FBI about what she had seen. She was still nervous, but she hid it behind her duel persona of Grizzly Kuma, the Wild Beast Duelist.

She had been at the first Battle City, though she hadn't been qualified to play at the time, and had seen enough to know that things like that just _happened_ in tournaments, especially around Yugi Mutou.

And there was another issue: Yugi Mutou. Kuma had been a year ahead of the tiny duelist and his friends, but she hadn't been blind to the odd things that seemed to happen around Mutou during her last year of high school. Well known bullies going crazy, falling into comas, or winding up dead, all after he had started wearing that creepy pyramid. She had seen him duel, had seen that stone tablet at the Domino Museum, and was convinced that Mutou was possessed by an ancient Egyptian vengeance demon haunting the pyramid.

But Kuma couldn't tell the FBI agents those sorts of things. She couldn't tell them about Mutou, and would in fact prefer that the Americans stayed as far away from the King of Games as possible. Unfortunately, she knew that the later was unlikely, as Mutou tended to be right in the middle of situations like this. The best she could do was to try to convince the agents to allow Battle City to continue without interference.

Gathering up Mother Grizzly, Kuma began shuffling the cards again. "You want to know about the dead man," she said, watching the Americans as cards flew beneath her fingers.

"If you can tell us what you saw, it could help us in our investigation," the older one, Agent Rossi, explained.

Kuma drew a card, knowing what it was even before she saw it. Beaver Warrior. "I saw light first," she said, shuffling the deck again.

"What light?" the younger agent, Reid, asked.

"The light of active Duel Disk," the duelist answered. She drew again. Silver Fang. "It is why I left the hotel. I thought it was a duel. I wanted to see the competition." Kuma shuffled again.

"And when you got there?" Agent Rossi asked.

"It was dark. The duel was over." Another draw. Amazoness Tiger. "There was a fire. Small." Shuffle. Draw. A field spell, Forest. "I saw him. It. The body." A trap card this time, Des Counterblow.

"Did you see anyone else?" Agent Rossi prompted. "Did you hear anything?"

"No." Kuma's hands pause in their shuffling as she frowned. " _Ano_ … There is something I do not understand…" She resumed shuffling, drawing comfort from her cards.

"Anything you can tell us can help," Reid assured the young duelist.

Another draw. Big Koala, one of Kuma's strongest monsters. She drew confidence from the powerful Beast and took a deep breath. "Why are you here, really?" she demanded. "Every duelist knows that to play the game is to gamble with your life and soul. His life points were zero; he had lost the duel after betting his life. He was weak, and Duel Monsters is no game for the weak."

"Five people are dead, their hearts cut out and burnt," Agent Rossi said. "Why wouldn't we be here?"

"People died in Duelist Kingdom and the first Battle City, too." Kuma shrugged, shuffling her deck again. "Many of us would not play if there was not that hint of danger."

"I highly doubt that the people here died from their duels," Agent Rossi informed Kuma. "The coroner determined that the victims were still alive when their hearts were cut out."

" _Nani!_ " Kuma slipped back into Japanese for a moment, her shuffling stopped. "That does not make sense, that is not how it works." Not unless it hadn't been their lives on the line, but their souls. Soulless, Donally- _san_ would have been helpless against his attacker.

"That's not how what works?" Reid pressed.

"There is…sort of an unspoken rule," Kuma answered. "If a duel is over, it is over, unless a penalty was agreed to beforehand. Once that penalty happens, that is the end. There is not supposed to be a punishment after the penalty."

Kuma had researched the Sennen Items after Battle City Domino, wanting to know more about the terrifying powers being thrown around by every duelist that held one. From what little she had found, the magic of the Items had rules, and would turn upon those who broke them.

If there was someone capable of breaking those rules, then the FBI wasn't likely to stop them. Not if this Battle City turned out like Domino's, where law enforcement had wisely stayed out of the conflict between duelists.

"And you don't think that Brian Donnelly's death was his penalty?" Agent Rossi remarked. "Why is that?"

Kuma didn't say anything, having already told the Americans more than she had planned. There was something about them, though, that made them seem like people she could trust with that information. Agent Rossi's calm and understanding countenance encouraged trust, and Agent Reid felt so much like a fellow duelist, it was hard to remember that he worked for the US government.

They didn't deserve to die, and Kuma wouldn't be able to face herself in the mirror if she didn't at least _try_ to warn them off.

"You should let this go," she advised the agents. "This is a duelist matter, like Battle City Domino. Once the tournament is over, the killings should end."

"There's a serial killer targeting duelists out there." Rossi was flabbergasted. "Aren't you worried at all?"

"I am a strong duelist, and I believe in my deck," Kuma replied. "Eventually, this killer will challenge someone better than them, and lose." She gathered her cards, gently tapping the edges on the table to square the deck. "Are you finished with your questions?"

"For now," Agent Rossi said, giving Kuma a scrutinizing look. "If we have any more questions, we'll let you know."

Kuma nodded, putting her deck back into its holder. She stood up, then paused. "If you want the other duelists to talk to you, I suggest you offer to play a game with them," she turned to Reid, "Agent Reid."

"Why me?" Reid wanted to know.

"Because gamers know gamers." With that insight, Kuma left the room.


	4. Ei Teopixqui

In his hotel room, a young man held up various accessories as he stood in front of the room's mirror. Each strap, chain, and armband he chose was summarily rejected, a new one chosen in its place only to be put aside as well. This was Yugi Mutou, the famous King of Games.

"You're worried," a confident voice stated in Japanese.

The young man turned. On the bed lounged the teen's twin, dressed in a matching outfit.

"Kaiba- _kun_ called to tell us that another body was found last night, and that he wants all of the tournament's duelists to go to the Convention Center to _talk to the FBI!"_ The teen's voice went shrill at the end, and he ran his fingers through his spiky hair.

"And what is the problem, _aibou_?" The other teen slid off the bed and joined his twin. "You haven't done anything wrong. Just tell them the truth: that you have nothing to do with the deaths." He inspected the items that his partner had discarded.

"They're _feds!_ " Yugi retorted, putting on the accessories that his twin pointed out. "You've seen the movies, other me. Americans are crazy!"

"Hmm." The other Yugi paused. "But that's not the only reason why you're worried."

Yugi bit his lower lip, cupping between his hands the golden pyramid pendant that hung from around his neck. "Every time something like this happens, it's because someone is after the Puzzle. We've managed to beat everyone so far, but what if I lose you this time?"

"You won't," the other teen stated. "Have confidence in our skills, and in our deck." He grasped Yugi's hand and squeezed. "Have you forgotten my promise already? I plan on being at your side forever."

"I remember." Yugi looked down at their joined hands and squeezed back. "Thank you."

Yugi startled at the sudden pounding on his hotel room door. _"Yugi! Are you ready to go, yet?"_

"Ah! Coming, Anzu!" Yugi called back. He grabbed his deck belt, already carrying his deck, and put it on before grabbing his Duel Disk and hurrying out the door.

The mirror reflected an empty room, the other Yugi never once casting an image on its silvered glass.

* * *

In a darkened room, a figure moved about. A cactus thorn was pressed deep into the pad of an index finger before being discarded. A bead of crimson blood welled up from the puncture and allowed to drop onto the surface of a small obsidian round, marring it's highly polished surface.

The bloodied mirror was lifted to a shadowed face, the room's meager light barely revealing the wide, painted bands of black and yellow. Painted lips parted to exhale a warm breath, clouding the mirror's surface. In a low, husky voice, the painted figure spoke in an ancient language.

"Oh man, oh lord, oh Master! Oh god, thou who stands at the shoulder. Thine faithful supplicant beseeches thee, receive this humble sacrifice and grace thy servant with thine presence."

As the condensation on the obsidian mirror faded, the drop of blood began to smoke, forming a tiny cloud above the reflective surface.

"My servant," the cloud whispered. "My strength grows with every heart thee offers in my name. But it is not enough!"

"Soon, my lord! The signs are clear: the Morning Star has returned, restoring the golden pyramid and bringing the Sun out of darkness!" The voice of the painted figure rose in their excitement. "I will tear out the heart of the Precious Twin, casting the Sun into eternal darkness. The age of Quetzalcoatl shall end, and your reign, oh Tezcatlipoca, shall begin."

"Good," the cloud hissed. "Do not fail me. I gave thee thy powers, I can take them away."

"Fear not, master. The Precious Twin holds the power of dead gods, their worshippers dust. The gods in my deck live still, cloaking themselves in the trappings of Christianity. We will not fail thee," the figure vowed.

"See that thou shan't, or it shall be _thy_ heart to be offered, instead." The cloud dissipated, the dark presence it had summoned fading away.

"It shall be done."

* * *

In an otherwise empty corridor in the San Diego Convention Center, two figures strode side by side. The young man in the sweeping forest green longcoat towered over his companion, a duelist of short stature and wild, multicolored hair. The confidant stance made it clear that the shorter duelist was the other Yugi, known sometimes as Yami Yugi, or simply as Yami. His taller companion was Seto Kaiba, the CEO and president of Kaiba Corp.

"Is there a reason why you wanted to talk to me away from my friends, Kaiba?" Yami asked.

"Outside of the fact that I find your friends to be utterly beneath me in every way?" Kaiba retorted.

Yami grit his teeth but stayed silent, unwilling to rise to Kaiba's bait.

"How much do your friends know about what you used to do?" Kaiba suddenly asked.

"Excuse me?"

"What do your friends know about what you did in the months before Duelist Kingdom?" Kaiba clarified.

Yami bit his lip, feeling his partner's presence and curiosity. His innocent and forgiving partner, who never would have approved of most of his darker half's actions during those early months. Yugi had never asked about what had happened during those blank stretches of memories, and Yami had never volunteered the information. He would have liked his partner to remain ignorant, but he had a feeling that Kaiba had a good reason to ask.

"Not much," the spirit finally admitted. "Outside of those incidences that they were there for, that is, and even then they weren't aware of everything that was going on. Until our duel in Duelist Kingdom, my partner was unconscious whenever I was in control, so even he doesn't know."

"You probably don't know this, but your actions _should_ have brought you to the attention of the authorities," Kaiba informed his rival. "It took me a lot of time and effort to bury it as much as possible."

Yami was shocked. "You… But why?"

Kaiba scoffed. "Don't think I did it out of any sort of fondness for you or the other Yugi. I'd just rather you not go to jail before I finally defeat you in Duel Monsters."

The spirit smirked. "Of course." He then frowned. "But if it's already been taken care of, why bother telling me?"

"Because I couldn't cover it all up completely," Kaiba snapped. "Anybody with the necessary talent can find some of it with a bit of effort if they looked. And they will be looking."

"The FBI," Yami realized. " _Aibou_ said that they wanted to talk to all the duelists in the tournament."

Kaiba sighed, pinching the bridge of his nose. "And that's another issue. When they interview you, you can't switch places with the real Yugi. They'll notice it immediately."

" _Aibou_ 's friends didn't notice for months until he told them, and they knew him for years," argued Yami.

"And I barely knew Yugi at all, and I figured it out in minutes," Kaiba countered. "We're not just dealing with the FBI, we're dealing with the FBI's Behavioral Analysis Unit. They're profilers, and they've sent the best team in the unit. They have an agent who makes even _my_ intelligence seem average in comparison, and a tech analyst skilled enough to make me work to keep her out of my computers."

"What's this? Seto Kaiba admitting that there's someone smarter than him?" Yami mocked.

"Doctor Spencer Reid had three Ph.D.'s before he turned twenty-one," explained Kaiba. "He's a prodigy, practically destined for the BAU, with an eidetic memory and an IQ over 140. The FBI wanted him so badly, they waived the minimum age requirement, and he went straight into the BAU at twenty-two. I'd be a fool to ignore someone like that, and I'm far from being a fool."

For a few moments, Yami was silent. "You're worried," he said at last.

"There's a madman on the loose at one of my tournaments, again," Kaiba hissed. "Which means that Mokuba is in danger, _again._ I'm not worried, I'm angry, and I don't want the FBI messing this up because they're too focused on you and your magic split personality than on the actual murderer."

"I'll try not to switch, Kaiba, but I can't promise not to," Yami said, "and if these people are as perceptive as you say, they're just as to notice if Yugi doesn't act the way we usually do during our duels."

"I had considered the possibility," Kaiba admitted. He sighed. "I suppose all we can hope is that the FBI thinks that you just have a dueling persona, which isn't that uncommon among duelists."

Kaiba continued, "I was supposed to have been meeting with the unit chief, Agent Hotchner, a while ago. I sent Mokuba to greet them when they arrived, but I'll have to personally speak to them eventually."

"Then go," Yami encouraged. "I'll head back to my friends and pass on the warning."

"Humph, you better," Kaiba snorted. "I want this mess over with before it completely ruins my tournament." He turned away from the Duel King. "You better not get yourself killed by this bastard before I finally crush you myself," he said, walking away without giving Yami a chance to reply.

Yami sighed and shook his head as he watched Kaiba turn a corner, the tails of his coat snapping in his wake. Some things never changed, it seemed, including Kaiba's tendency towards theatrics. Chuckling quietly, the spirit turned back the way they had come, eager to get back to his friends.


End file.
